Performance improvement of a p-Cu2O nanocrystal photocathode with an ultra-thin silver protective layer.

A Ag film with 10 nm thickness is deposited on a directionally grown Cu2O single crystal photocathode by high power impulse magnetron sputtering (HiPIMS). The continuous Ag film not only forms a dense proton isolator, but also constructs a Schottky junction with Cu2O to accelerate the transportation of photo-induced electrons. After optimization, the photocathode exhibits much-improved activity and stability versus the unmodified one, and over 98% stability (state-of-the-art) remains after 5 h of light-chopping chronoamperometry. The sustained photocurrent density is 4.0 mA cm-2 at 0 VRHE.